1. Field of the Invention
The present invention relates to a bicycle sprocket wheel unit and a mounting unit to which the sprocket wheels are mounted, and more particularly to a sprocket wheel unit used for front wheel and rear wheel.
2. Descriptions of Related Art
The conventional sprocket wheels used on bicycle front wheel and the sprocket wheel unit used on bicycle rear wheel generally are made of a mediate to low carbon steel plate which is about 1.75 to 3.2 mm thick and made by the steps of pressing, teeth formation, heat treatment, grinding, electro-coating and surface treatment. Some sprocket wheels having a complicated structure require an expensive method such as forging or CNC machining. It is noted that sprocket wheels with larger radius and more teeth usually have higher manufacturing standard. The quality of the sprocket wheels may not meet the expected standard due to improper treatment in any one of the steps.
US 2012/0196711 discloses a sprocket wheel used on rear wheel in the form of an integral ring plate. The sprocket wheels numbered 11, 12, 13 are categorized as big sprocket wheels, and the sprocket wheels numbered 14, 15, 16 are categorized as small sprocket wheels. It is more difficult to manufacture the big sprocket wheels than the small sprocket wheels. These sprocket wheels are connected to the mounting unit at even space and fixed to the rear hub. Spacers are placed between the sprocket wheels.
U.S. Pat. No. 5,194,051A discloses a mounting unit which has multiple arms extending radially therefrom and each arm has stepped faces so as to fix multiple sprocket wheels to the stepped faces. The mounting unit is made by way of forging and has higher manufacturing cost and requires a longer manufacturing time.
The present invention is intended to provide a bicycle sprocket wheel unit and a mounting unit therefor to eliminate the shortcomings mentioned above.
The sprocket wheel unit can be used for both the front wheel and the rear wheel. The mounting unit is used for the sprocket wheels used on both of the front wheel and the rear wheel.